1. Field of the Invention
The present invention relates to multi-circuit brake systems for motor vehicles.
2. Description of Related Art
Such multi-circuit brake systems, particularly of the hydraulic type, have gained ground in the vehicle manufacture for reasons of efficiency and reliability through redundancy. In response to the actuation of the brake pedal, hydraulic fluid in a main brake cylinder is typically compressed and displaced to the hydraulic brake circuits.
Modified constellations may result, for example, in that additional deceleration means such as connected generators in the form of the vehicle's electric generator or an electric drive motor operated as generator are integrated in the brake system in hybrid vehicles. This allows for recuperative braking, for example, which, for one, does not stress the brake and for another, recovers energy from the kinetic energy of the vehicle during braking. However, when combining the deceleration effects by corresponding active power components on the one hand and the wheel brakes on the other, considerable problems must be solved. The deceleration effect of regenerative active power components may be variable, in particular, so that the driver must compensate for corresponding changes in the rate of deceleration by stronger or weaker actuation of the brake pedal.
Control devices for controlling or regulating elements of a braking system are basically known in a wide variety of types. They are used, for instance, in ABS systems, in traction control systems, in the dynamic electronic stabilization of a vehicle during cornering, or also as aid in unbraked cornering by automatic application of the brakes at a wheel on the inside of the curve.
From German patent application document DE 102006020890, a brake device having a particularly compact design of a hydraulic block is known.
From German patent application document DE 102006020520, a brake system having a brake-limiting, correspondingly controlled valve is known.
From published German patent application document DE 4128087 A1, a brake pressure regulating system for a vehicle is known, by which an underbraked rear axle is prevented when braking during cornering. The brake pressure at the front axle is specified by the driver, and the brake pressure at the rear axle is regulated as a function thereof.
It is basically also known to distribute the brake force such that, if possible, heavy braking of the vehicle is achieved while taking the adhesion utilization into account; in this context, it also is possible for wheels that are statically and/or dynamically more heavily loaded to be braked to a correspondingly greater degree.
From published European patent document EP 0173954 B1, a system is known in which the brake pressures for individual brakes are ascertained in a stored vehicle-specific characteristics map with the aid of a reference mass for the vehicle and the driver-specified nominal deceleration. The determined brake pressures are applied at the brakes and, if necessary, are adjusted if the vehicle deceleration deviates from the nominal value, until the nominal deceleration has been achieved.
From published German patent application document DE 3313078 A1, a brake pressure regulation device is known, which determines the wear of various wheel brakes and takes it into account, so that even wear of the individual wheel brakes is achieved in the long term.
From German patent application document DE 102005046606, a brake system is known in which an individual brake circuit is assigned to one of the axles of a vehicle, so that a traction control device as well as an electronic stability control device may be provided in one brake circuit exclusively, which minimizes the constructive overall investment.
Finally, from published German patent application document DE 10316090 A1, a brake system is known which has a plurality of brake circuits, which basically act hydraulically and act on friction brakes of individual wheels; furthermore, it has a generator or an electric drive motor which can be operated as generator and be used for deceleration in addition. A control device is provided in order to optimize the brake force distribution to all individual wheels while taking different variables pertaining to driving dynamics into account.